Non-Invasive Quantification of Ventricular Contractility, Arterial Elastic Function and Ventriculo-Arterial Coupling from a Single Diagnostic Encounter Using Simultaneous Arterial Tonometry and Magnetic Resonance Imaging.

Optimal assessment of cardiovascular performance requires simultaneous measurement of load independent left ventricular (LV) contractility, arterial function and LV/arterial coupling. We aimed to demonstrate feasibility of non-invasive ventricular pressure-volume and aortic pressure-flow-impedance measurements using simultaneous arterial tonometry (AT) and cardiovascular magnetic resonance imaging (CMRI). 21 consecutive patients referred for CMRI were enrolled to undergo a simultaneous AT and CMRI protocol. A CMRI compatible AT apparatus provided aortic end-systolic pressure, taken to be equivalent to LV end-systolic pressure in the absence of aortic stenosis. CMRI provided LV volume and aortic flow at the time of pressure acquisition. Pressure-volume relationships were determined and correlated to traditional parameters of LV function including ejection fraction and circumferential strain. Aortic pressure-flow relationships were used to determine aortic characteristic impedance and systemic vascular resistance. Simultaneous AT and CMRI permitted measurement of LV end-systolic elastance, preload recruitable stroke work, arterial elastance, aortic characteristic impedance and systemic vascular resistance. Absolute values were within the expected range for our cohort, were highly reproducible and showed appropriately directed correlation to traditional parameters. Non-invasive assessment of LV pressure-volume and aortic pressure-flow relationships are both feasible and reproducible using simultaneous AT and CMRI. Methods permit assessment of load independent LV contractility, arterial function and LV/arterial coupling from a single non-invasive diagnostic encounter.